The present application claims priority to Japanese Application(s) No(s). P2000-281023 filed Sep. 14, 2000, and P2000-36069 filed Nov. 28, 2000, which application(s) is/are incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention relates to technology for shortening the manufacturing process for semipermeable liquid crystal display devices by forming surface irregularities on the reflective electrode simultaneously with forming openings on the permeable section of the pixel in the interlayered insulating film on silicon film formed with the source and drain of the thin film transistor.
2. Description of the Related Art
The drive side of the TFT (thin film transistor) substrate of the active matrix type semipermeable liquid crystal display device of the related art having a reflective electrode composed of a reflective diffusion plate formed with surface irregularities, and also having a transparent electrode made from transparent conductive film in the transparent section of the pixel is fabricated as shown in FIG. 12A through FIG. 12I. The process for fabricating liquid crystal devices having a pixel structured from a bottom gate type TFT is shown in FIG. 12A through FIG. 12I, however a pixel with a top gate type structure TFT is fabricated in basically the same process.
As shown in 12A, a metallic film is first formed on a transparent substrate 1, and a gate G and an auxiliary capacitor electrode Cs formed by etching using photolithography, a gate insulation film 2 deposited, and a polysilicon film 3 formed.
Next, to prevent doping of impurities into the channels during impurity doping of the source and drain regions, a stopper 4 is formed to self-align with the gate G on the polysilicon film comprising the channels, and the source region and drain region are doped with impurities.
Islands shapes are then formed separately on the polysilicon film 3 using the photoresist process and the etching process, and a low temperature thin film transistor (TFT) is formed.
The interlayered insulator film 5 is formed next in FIG. 12B. Next, in order to form contact holes and an opening for the pixel transparent section, a photoresist layer 6 is first of all formed on the interlayered insulator film 5, and the photoresist layer 6 is patterned in FIG. 12C by the photolithographic method using as a pattern~mask, to form contact holes and an opening for the pixel permeable section T as the photomask. Etching is then performed using the interlayered insulator film 5 as the etching mask, and contact holes H1 and the pixel permeable section T opening are formed (FIG. 12D) .
The metallic film is then formed using a stopper etc. A signal line and source electrode S1 connecting to the TFT source S by way of the contact hole H1 are formed by etching, and a drain source electrode D1 connecting to the drain D of the TFT by way of the contact hole H1 is formed by etching as in FIG. 12E.
The irregularities forming the base of the surface irregularities of the reflecting electrode having a reflective diffuser function are formed as described next using two layers of photoresist material. A first layer 7 forming the basic structure of the irregular shape is formed by photolithography using the photoresist material in FIG. 12F. The photomask is used to make openings for a second collector hole 2 and pixel permeable section T for conduction between the source electrode S1 and drain electrode D1. Next, a second layer 8 for improving the reflection is formed as shown in FIG. 12G by photolithography using a photoresist material identical to the first layer 7. The mask is utilized to make openings for the third collector hole H3 and pixel permeable section T for connection with the drain electrode D1. A surface irregularity (rough) section is in this way formed from the first layer 7 and second layer 8 structure.
A transparent conducting film 9 constituting the transparent electrode of the pixel permeable section T is next formed by sputtering, etc. This transparent conducting film 9 connects to the drain electrode D1 and contact hole H3 as shown in FIG. 12H. The transparent conducting film 9 also forms the reflecting section of the pixel and may also be used as the base material (or underlayer) of the reflecting electrode.
A metallic film such as aluminum or silver having high reflectivity is next deposited on the reflecting section R of the pixel, and a reflecting electrode 10 is formed as in FIG. 12I by photolithography.
The drive side of the TFT substrate is in this way completed. A polarizing film is coated on this TFT substrate, and opposing substrate formed of the color filter and opposing transparent electrode, and a polarizing process is performed, both the substrates are overlapped on each other using a gap material to maintain a suitable gap between the substrates, liquid crystal injected and sealed to obtain the liquid crystal display panel.
In the fabrication process for the drive side substrate of the TFT (thin film transistor) substrate of the active matrix type semipermeable liquid crystal display device of the related art as shown in FIG. 12A through FIG. 12I, a seventh and an eighth layer are formed from photoresist material to apply specified surface irregularities (rough shape) to a reflecting electrode 10, and since ultimately a total of three insulating layers including an interlayered insulator film 5 are formed between the reflecting electrode 10 and the silicon film forming the source S and drain D of the TFT, that require patterning processes by respective lithographic methods, and further since a source electrode S1, a drain source electrode D1, and a reflecting electrode 10 must be formed by separate processes, the problem occurs that many man-hours are required and the manufacturing cost is high.
Whereupon, the present invention has the object of providing a simple and manufacturing process for an active matrix type semipermeable liquid crystal display device yielding improved productivity.
To achieve the above objects, in the manufacturing process for the semipermeable liquid crystal display device by the inventors of the present invention, a photoresist layer is formed on the interlayered insulator film on the silicon layer forming the source and drain of the TFT device, and corresponding surface irregularities are simultaneously formed on the reflecting electrode of the pixel reflecting section, and opening for the pixel transparent section on the photoresist layer, by patterning with photolithographic methods utilizing a designated photomask on that photoresist layer, so that by forming surface irregularities (rough shapes) on the pixel reflecting section simultaneous with forming an opening on the transparent section of the pixel in the interlayered insulator film, a greatly shortened manufacturing process for liquid crystal devices can in this way be obtained.
The present invention in other words, provides a manufacturing method for an active matrix type semipermeable liquid crystal display device consisting of an interlayered insulator film on the silicon layer forming the source and drain of the TFT, a reflecting electrode formed with surface irregularities (rough sections) on the interlayered insulator film in the pixel reflecting section, and a transparent electrode consisting of a transparent conductive film on the pixel transparent section, wherein in the forming and processing of the interlayered insulator film in the following processes A through D;
A: is a process for forming an interlayered insulator film on a silicon layer forming the source and drain of the TFT;
B: is a process for forming a photoresist layer on the interlayered insulator film;
C: a process for patterning the photoresist layer by the photolithographic method wherein, in a process using a mask formed with a pattern below the resolution limit in the section forming the reflecting electrode, the photoresist layer is utilized as the photomask, so that the photoresist layer corresponding to transparent section of the pixel and the section forming the contact holes in the interlayered insulator film of the drain and source can be completely removed, and so that surface irregularities can be formed in the photoresist layer corresponding to the section forming the reflecting electrode,
D: a process using the photoresist layer patterned in process C as the etching mask for completely etching an opening in the interlayered insulator film for the transparent (permeable) section of the pixel and the section for forming the contact holes, and for etching the interlayered insulator film so that surface irregularities are formed in the interlayered insulator film of the section forming the reflecting electrode.
The invention further provides a manufacturing method in particular comprising the following sequential processes performed after the D process wherein,
E is a process for simultaneously forming from a metallic film; signal wiring and a source electrode connecting with the source by way of contact holes, and a reflecting electrode and drain electrode connecting to the drain by way of contact holes and signal wiring,
F is a process for patterning a protective film in a region containing the pixel transparent section and reflecting section, so that the section forming the contact hole on the drain electrode as well as the section for the transparent section of the pixel have openings,
G is a process for forming a transparent conductive film so as to comprise a pattern containing the pixel transparent section and reflecting section, and connect the transparent electrode and reflecting electrode by way of the contact holes, and further in the F process, a patterning method is provided for forming a protective film from the photoresist layer, characterized in that patterning is by the lithographic method, and in a process using a mask formed with a pattern below the resolution limit in the section for forming the reflecting electrode, the protective film is utilized as photomask, so that a protective film corresponding to the section forming the drain electrode and permeable sections of the pixel can be completely removed, and surface irregularities (rough sections) can be formed in the protective film corresponding to the section forming the reflecting electrode.
The invention further provides a manufacturing method comprising the following sequential methods performed after the D process wherein,
E is a process for simultaneously forming from a metallic film; signal wiring and a source electrode connecting with the source by way of contact holes, and a reflecting electrode and drain electrode connecting to the drain by way of contact holes and signal wiring,
Gy is a process for forming a transparent conductive film so as to comprise a pattern containing the pixel transparent section and reflecting section, and connecting the transparent electrode and reflecting electrode,
The invention further provides a manufacturing method comprising the following sequential methods performed after the D process wherein,
Ex is a process for simultaneously forming a pattern of transparent conductive film wherein said pattern contains signal wiring and a source electrode connecting with the source by way of contact holes, and a permeable and reflecting section of a pixel, and a drain electrode connecting to the drain by way of contact holes,
Gx is a process for forming a reflecting electrode from a film composed of metallic film, and connecting to the reflecting electrode and transparent electrode.
The present invention further provides an active matrix type semipermeable liquid crystal display device consisting of an insulation layer on a silicon film formed as the source and drain of the TFT, a reflecting electrode formed with surface irregularities on the insulator layer in the reflecting section of the pixel, and a transparent electrode film made from transparent conductive film in the transparent section of the pixel wherein, the insulator layer is formed from one layer of insulator film.
In a liquid crystal device in particular wherein, the transparent conducting film of the pixel transparent section is extended onto the reflecting electrode, the transparent conducting film connects with the reflecting electrode, and further, a protective film is formed between the reflecting electrode and transparent conducting film, and the cell gap of the liquid crystal display cell is set at xc2xdxcex in the permeable section and xc2xcxcex in the reflecting section, and surface irregularities are formed in the transparent conducting film on the reflecting electrode in this state.
A liquid crystal device of the present invention is provided wherein the transparent conducting film and reflecting electrode are sequentially laminated on the reflecting section of the pixel, and the reflecting electrode and transparent conductive film are connected.
In the manufacturing method for the active matrix type semipermeable liquid crystal display device of the present invention, a photoresist layer is formed on the interlayered insulator film on the silicon film of which the source and drain of the TFT are formed, and by patterning that photoresist layer by utilizing a designated photomask, an opening with a shape corresponding to the transparent section on the pixel and surface irregularities corresponding to the reflecting electrode on the reflecting section of the pixel are formed on the photoresist layer, and by next etching the interlayered insulator film using the photoresist layer as an etching mask, surface irregularities (rough shapes) can be formed on the reflecting electrode of the reflecting section of the pixel and an opening formed in the permeable section of the pixel on the interlayered insulator film. The laminating processes for the photoresist layer required in forming the surface irregularities on the reflecting electrode in the active matrix type semipermeable liquid crystal display device of the related art can therefore be reduced, and the source electrode, signal wiring, drain electrode and reflecting electrode formed by separate processes in the related art can be simultaneously formed by forming one metallic film so that the manufacturing process for a liquid crystal device can be greatly simplified, and productivity can be boosted.
Also in the present invention, the transparent conductive film is extended to the reflecting electrode, and the transparent conductive film and reflecting electrode are electrically connected, so the silver forming the reflecting electrode in the liquid crystal display cell is transferred to the opposing substrate and the crystallization phenomenon can therefore be prevented.
Further in the present invention, by forming a protective film between the reflecting electrode and the transparent conducting film, and by adjusting the thickness of that protective film, the optical characteristics of the reflecting section and permeable section of the pixel can easily be optimized.